[NOIP2017 普及组] 图书管理员

#include <bits/stdc++.h>
using namespace std;
int n, q;
int book[1005];
int ten[15]; // 预处理 10^i
int main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);
    ten[0] = 1;
    for (int i = 1; i <= 8; i++)
        ten[i] = ten[i - 1] * 10;
    cin >> n >> q;
    for (int i = 1; i <= n; i++)
        cin >> book[i];
    while (q--)
    {
        int len, num; // 需求码长度和需求码
        cin >> len >> num;
        int ans = -1;
        for (int i = 1; i <= n; i++)
            if (book[i] % ten[len] == num)
            {
                if (ans == -1 || book[i] < ans)
                    ans = book[i];
            }
        cout << ans << "\n";
    }
    return 0;
}